A pressure sensor device disclosed in JP-A-7-243926 is shown in FIG. 6. A connector case 3 (a first case) and a housing 7 (a second case) are fixed together, and a sensing chamber 10 that has a predetermined internal pressure is defined by the case 3 and the housing 7. More specifically, a well 30 provided in the case 3 is partitioned by a metal diaphragm 8 that is welded to the housing 7 and a closed space is formed as the chamber 10. The chamber 10 contains oil 11, which is a pressure transmission medium. A pressure of the oil 11 is maintained at a predetermined level.
A sensing element 1, which is a sensing portion of the pressure sensor device, is provided in the chamber 10 and fixed to the well 30 to sense the oil pressure. The sensing element 1 is electrically connected to connector pins 4 arranged in the connector case 3 via wires 6.
In such a pressure sensor device, a measuring pressure is applied to the metal diaphragm 8 via a pressure application hole 72, and the oil pressure in the chamber 10 varies. An output signal corresponding to the variation in the oil pressure is outputted from the sensing element 1 via the connector pins 4.
The case 3 is fitted to an open-end of the housing 7, a rim 75 of which is in a straight shape as shown in chain double dashed-line in FIG. 6. While fitting the case 3 to the housing 7, the sensing element 1 and a predetermined volume of the oil 11 are held in the well 30. Then, a predetermined amount of force is applied to the rim 75 so that the housing 7 is crimped to the case 3. A closed space, which is the chamber 10, is defined.
The oil pressure in the chamber 10 after the housing 7 is crimped to the case 3 varies according to a cubic capacity of the chamber 10. The cubic capacity of the chamber 10 varies according to a size of the well 30, a shape of the metal diaphragm 8 after the welding, the volume of the oil 11, and other factors. Since the sensor element 1 senses the oil pressure in the chamber 10, the output of the sensor element 1 may be off a target level. This reduces a sensitivity of the sensor device, resulting in a problem not only for pressure sensors but also for sensors which sensitivity is affected by a force applied to cases for crimping.